TECHNOLOGY AREA(S): Space Platforms
OBJECTIVE: Develop a model of the outer zone of Earth’s radiation belt that is suitable for operational specification of electron flux levels.
DESCRIPTION: The outer zone of Earth’s radiation belt can be defined as locations in the magnetosphere where the geomagnetic L parameter is greater than 3, corresponding to altitudes of hundreds of kilometers (inclined Low Earth Orbits) to over 35,000 kilometers (Geostationary Orbit and beyond). This zone contains a highly variable population of electrons at relativistic energies (corresponding to greater than 500 kiloelectron-volts) that can be hazardous to spacecraft. The Secretary of the Air Force has mandated pre-Milestone B satellite programs as of March 2015 incorporate an Energetic Charged Particle (ECP) sensor to support space hazard assessment and space situational awareness. In order to accelerate the deployment of this capability, models allowing accurate estimates of energetic charged particle flux will aid in providing complete coverage, and couple with efforts to deploy hosted ECP sensors on commercial platforms. The outer zone population is dynamic and driven, influenced by changes in the electromagnetic field at many length- and time-scales . Recent simulation efforts largely focus on capturing one or more aspects of this system with a combination of physical modeling and data assimilation. This has largely been limited by a lack of suitable data sources that cover the spatial region of interest. The recent release of electron flux data from the GPS fleet could be transformative to data assimilative modeling efforts . The extensive spatiotemporal coverage of these data (over a decade of data from 6 MEO orbit planes with 6 satellites each) can greatly enhance the training and execution of models that can ingest it. This is true for a variety of modeling approaches: machine learning, empirical or applying a Kalman filter to a physical model [3, 4]. Regardless of technical approach employed, the resulting model should capture the dynamic and driven nature of the outer zone electrons as reflected in flux levels at specified energy ranges, informed by ECP sensor requirements.
PHASE I: Prototype model and source code, scientific validation, and roadmap to development required for operational deployment.
PHASE II: Prototype model and source code demonstrating needed operational capabilities suitable for V&V, documentation, and test suite.
PHASE III: Model suitable for use by military, civil, and commercial space organizations.
1: Shprits, Y. Y. et al. Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts. Nat. Commun. 7:12883 doi: 10.1038/ncomms12883 (2016).
2: Morley S.K., J.P. Sullivan, M.R. Carver, R.M. Kippen, R.H.W. Friedel, G.D. Reeves, and M.G. Henderson (2017), Energetic Particle Data from the Global Positioning System Constellation, Space Weather, 15, doi:10.1002/2017SW001604.
3: Reeves, G. D., Y. Chen, G. S. Cunningham, R. W. H. Friedel, M. G. Henderson, V. K. Jordanova, J. Koller, S. K. Morley, M. F. Thomsen, and S. Zaharia (2012), Dynamic Radiation Environment Assimilation Model: DREAM, Space Weather, 10, S03006, doi:10.1029/2011SW000729.
4: Drozdov, A. Y., Y. Y. Shprits, K. G. Orlova, A. C. Kellerman, D. A. Subbotin, D. N. Baker, H. E. Spence, and G. D. Reeves (2015), Energetic, relativistic, and ultrarelativistic electrons: Comparison of long-term VERB code simulations with Van Allen Probes measurements. J. Geophys. Res. Space Physics, 120, 3574–3587. doi:10.1002/2014JA020637.
5: McCollough, James, White Paper on ECP Energy Range and Flux Requirements, 8 pages (uploaded in SITIS on 8/29/17).
KEYWORDS: Van Allen, Radiation Belt, Space Environment, Modeling, Physics, Data Assimilation